Packet switched wireless access networks contain AN (Access Network) elements that are connected to AR (Access Router) elements. Typically, an AR serves an MN (Mobile Node) via the AN which is presently serving the MN. Again typically, an AR performs the function of a mobility agent to support the network layer mobility of the MN. In the event of an inter-AR handoff of the MN within the same wireless technology or across different wireless technologies, the mobility agent for the MN switches from the source AR to the target AR. This results in a new link layer connection being established between the MN and the new AR.
The re-establishment of a new link layer connection with the target AN causes the link layers (e.g., the ARQ layer) of both the source AN and the MN to flush their outstanding transmit and re-transmit queues. The flushing of outstanding radio frames can result in a noticeable performance impact for the affected end-to-end applications, especially VoIP-based (voice over internet protocol) and PTT-based (push-to-talk) applications. Such packet loss may also cause a TCP (Transmission Control Protocol) sender to initiate congestion control by invoking the slow start procedure. This may, in turn, impact the end-to-end performance of the TCP-based application.
Therefore, a need exists for an apparatus and method that improves link layer handoff by addressing the packet-loss problem existing today.
Specific embodiments of the present invention are disclosed below with reference to FIGS. 1-5. Both the description and the illustrations have been drafted with the intent to enhance understanding. For example, the dimensions of some of the figure elements may be exaggerated relative to other elements, and well-known elements that are beneficial or even necessary to a commercially successful implementation may not be depicted so that a less obstructed and a more clear presentation of embodiments may be achieved. Simplicity and clarity in both illustration and description are sought to effectively enable a person of skill in the art to make, use, and best practice the present invention in view of what is already known in the art. One of skill in the art will appreciate that various modifications and changes may be made to the specific embodiments described below without departing from the spirit and scope of the present invention. Thus, the specification and drawings are to be regarded as illustrative and exemplary rather than restrictive or all-encompassing, and all such modifications to the specific embodiments described below are intended to be included within the scope of the present invention.